This invention relates to the art of snowplows mountable on automotive vehicles and, more particularly, to plow blade lift mount assemblies for snowplow blade units.
It is of course well known that service station owners, farmers and other individuals use commercially available vehicles such as pick-up trucks as snowplows. In this respect, such a vehicle is provided with a plow blade unit support structure which is mounted on and beneath the vehicle frame rearwardly of the front of the vehicle, and a plow blade lift mount assembly which is mounted on the front end of the vehicle and, for example, on the bumper thereof or a special cross member between the front ends of the vehicle frame members. The plow blade unit generally includes a frame assembly supporting a plow blade forwardly of the vehicle and having an inner end adapted to be releasably hitched to the support structure beneath the vehicle. The blade unit frame is interconnected adjacent the front of the vehicle with a vertically pivotal lift arm of the lift mount assembly which is actuated such as by a hydraulic cylinder and ram to achieve elevating and lowering of the plow blade relative to ground. Detachment of the plow blade unit advantageously enables use of the vehicle for personal and/or work oriented purposes other than snowplowing.
When such a plow blade unit is attached to a vehicle, the lift mount assembly serves primarily to elevate and support the plow blade above ground during transportation of the snowplow from one location to another as well as during a snowplow operation such as when the vehicle is moving backwards. When the blade is lowered to the ground in order to plow snow, the snowplowing forces are directed through the plow blade unit frame to the connection thereof with the vehicle frame. Thus, the maximum forces and stresses insofar as the lift mount assembly is concerned are applied thereto when the plow blade is elevated from ground. These forces and stresses result from the weight of the blade and the vertical bouncing of the blade during elevated transport thereof by the vehicle, which bouncing can transmit severe forces when the vehicle passes over a bump or a depression such as that resulting from a chuckhole in a street.
Lift mount assemblies heretofore provided for the foregoing purpose include one or more of a number of structural characteristics which are disadvantageous from the standpoint of weight, the magnitude and direction of forces applied to component parts thereof and to the vehicle on which they are mounted, aesthetics with respect to the vehicle, exposure to adverse environmental conditions and to potential physical damage during non-snowplow use of the vehicle, and cost from the standpoint of manufacture of the mount assembly and/or modification of the front of a vehicle to facilitate the attachment of the assembly thereto. More particularly with regard to such disadvantages, lift mount assemblies heretofore provided are mounted on the existing vehicle bumper, or on a special cross member between the vehicle frame members which either replaces or is provided in addition to the bumper, or are primarily mounted on one of the vehicle frame and bumper components and interconnected with the other by bracing. Generally, the lift arm mounting component or components of the lift mount assemblies extend vertically a considerable distance above the point of structural connection thereof with the vehicle and, most often, to a point at or just below the plane of the vehicle hood. Furthermore, the lift cylinder and ram components of the assembly are in most instances interconnected with the lift arm mounting member and the lift arm to provide an angular relationship therebetween which is disadvantageous from the standpoints of mechanical advantage and force application on the cylinder and ram components in connection with actuation of the lift cylinder to elevate and lower the plow blade. Examples of such arrangements are shown in Swiss Pat. No. 264,534 and U.S. Pat. Nos. 2,667,708 to Gjesdahl; 3,214,138 to Jocher et al; 3,401,008 to Standfuss; 3,456,369 to Leposky; and 3,987,562 to Dean et al.
It will be appreciated from the arrangements shown in the patents referred to above that, when the blades thereof are elevated, the vertically long lift arm mounting members cause considerable torsional stress at the points of connection between the mounting members and the vehicles as a result of the weight of the corresponding plow blade unit. Such torsional forces necessitate structurally heavy mounting members and supports therefor, and special structural interconnections therebetween such as multiple weldments in an effort to minimize damage and/or bending or breakage of the mounting member and/or its support components. Accordingly, the lift mount assemblies are either structurally complex, heavy, expensive to produce and/or cumbersome to install. It will be further appreciated from such prior art, and especially with respect to a construction such as that shown in the Swiss patent in which the lift arm mounting member structure and lift cylinder are behind a cross member at the front of the vehicle frame, that previous lift mount assemblies require a special construction or modification of the front end of the vehicle to accommodate the assembly, thus further adding to the cost and detracting from the aesthetic appearance of the vehicle front. It will be appreciated that any required modification of the vehicle front, such as to replace the original or standard bumper thereof with a special cross member, both increases the cost and detracts aesthetically. It will likewise be appreciated that any mounting on the standard bumper of a vehicle not only detracts from the aesthetic value, but more importantly, subjects the bumper to distortion and damage as a result of the forces applied thereto when the plow blade is transported in an elevated position.
With further regard to lift mount assemblies heretofore provided, all of the component parts thereof are intended to remain on the vehicle when the plow blade unit is removed therefrom. This is undesirable from the standpoint of the weight imposed on the front axle of the vehicle, especially in view of Federal Government restrictions on front axle loading. Moreover, such prior arrangements provide for at least the lift arm and a portion of the lift cylinder unit to project a considerable distance forwardly of the vehicle bumper or the cross member replacing the bumper. Such projecting parts are thus subject to damage or destruction, together with the lift arm mounting member and vehicle bumper and/or frame members should the vehicle impact against an object such as another vehicle. Moreover, these component parts are exposed year round to adverse weather conditions, thus increasing maintenance and replacement costs. Further, the component parts are of course visible and thus detract from the aesthetic appearance of the front of the vehicle when it is not being used as a snowplow. While arrangements such as those shown in the Jocker et al and Dean et al patents referred to above provide for collapsing the lift cylinder and lift arm into a stored relationship to reduce the extent of projection of the lift mount assembly forwardly of the vehicle during non-snowplowing use thereof, such stored relationship does not eliminate exposure of the component parts to environmental conditions, nor does it eliminate potential damage thereto should the vehicle impact with another object, or reduce the weight on the front axle of the vehicle. Moreover, such storage does little to improve the aesthetic appearance of the front of the vehicle relative to that which exists with the lift arm and cylinder in their use positions. A further problem in connection with such lift mount assemblies is theft, wherby leaving the lift arm and lift cylinder components on the vehicle whether stored or not, subjects the owner of the vehicle to a potential aggravation and financial loss resulting from such theft.
With regard to the aesthetic value of the vehicle mentioned hereinabove, it will be appreciated that the owner of such a vehicle often uses the same as a personal or family conveyance, whereby aesthetics are of considerable importance. A special cross member at the front of the vehicle to replace the standard bumper in order to support a lift mount assembly is thus obviously undesirable, as is the mounting of the lift mount assembly either directly or indirectly on the bumper. The latter not only detracts aesthetically but also subjects the bumper to damage or distortion which would further detract from the aesthetic value thereof. Still further, any special modification of a commercially available vehicle which is required to install a lift mount assembly is undesirable both from the standpoint of cost and aesthetics.